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Guys - I've had revo 5hr trial installed at Dialynx and have noticed after a few miles that the car "jumps" on full boost around 4k revs....I can only explian the "jumping" as boost cut off firing or perhaps a coil pack unhappy under the heavy load. I ran VAG-COM and there are no faults and on doing a map, the boost got really high (2.6bar over vacuum) around 4k revs, I was told to expect between 2.2 and 2.4. The car runs fine if you accelerate from say 1k revs in 2nd all the way until red line increasing the throttle slowly, but if I'm doing say 2.5/3k revs and floor it she jumps and hiccups like mad. You got any ideas? Obviously I don't want to have the full veriosn installed unless I can cure this. Would appreciate some assistance or tips on how to check the coil packs?
Thanks,
Rob

I would say you're hitting throttle cut. This is occuring because you're spiking over 1.55bar. I bet if you logged block 003 on the vagcom, you would see throttle position go from 100 down to around 30/40 when you feel the hiccup. Let us know what you find.

Ok - I'll check in a bit but how can I fix? I have turned N75 down as low as it will go. Dialynx altred somehting as I run optimax, perhaps if they reversed that it will help? Finally - is it good or bad that the car is boosting way beyond what was expected?

for most of us over in the States, we use one of two different things. You can run a manual boost controller in parallel with the N75 that will eliminate the boost spike, but still allow the N75 to control the rest of the boost throughout the rpm range. Second, we have TCD's (throttle cut defenders) which is basically a zener diode on the MAP sensor which fools the ECU into thinking you're not going over a set boost level(determined by which diode is used)

ah-ha. Thanks Imolavirus. I'm not that interested in the manual boost controller. But where would I find a TCD and how easy are they to fit? Appreciate your help. Still trying to get out to do that run with group 003....

you can email mike01s4@yahoo.com he can provide you with a tcd and some more info about them. But, I wouldn't count out the MBC so soon, i think it is a great option for just controlling boost spikes. You can set the MBC to say 18psi so when the turbos try to spike, once they hit 18, the wastegates will open. From there on to redline, the N75 will still have control over the wastegates. This also lets you leave the MAP sensor alone, because the throttle cut is used as a saftey control for boost leaks and other problems that would cause irregular boost numbers at the manifold.

Uuuuuuuuh, MBC's and TCD's again, OMG, is this tuning or tinkering or what???????? Tuning means letting the ECU be in control of everything, including boost and throttle control, WTF is this all about with piggyback solutions to fake the ECU into thinking everything is ok????

If you want to tune a car, you have to do it right, if you have to use any of these gizzmos, it means the ECU isn't doing its job properly, and 2.6 Bar on an S4 is just more than plain stupid, not only unsafe for the turbos. If you look at a compressor map for the S4 K03 turbos, you'll see that 2.6 pressure ratio means very low efficiency, which brings you nothing apart from a little more torque. Tuning isn't all about messing around and trying to get the most out of an engine, it does also have to do with knowing what an engine is, how it is supposed to run, thermodynamics, fluids flow, gas flow and so on. If you're trying to do too much, you'll either just simply loose power or turn the engine into a timebomb and eventually blow your turbos.

Some tuners might actually push their software too far just to help you go along the slippery slope of the €xpen$$iv€ upgrades quicker...

HTH,

Mihnea

Well obviously the tuning is having issues, so those are a couple ways to quick fix the problem. Never was it said that those were the best tuning options for the car, they are just ways to get around the tuning issues of the chip. I agree the TCD can be a downfall as it takes away some of the controls the MAP sensor has, but the MBC just to control the spikes isn't so bad. All its doing is preventing the spikes and the ECU still has control over via the N75. And, unlike the TCD, the ECU still has complete knowledge of what the current boost level is.

Tartan_Rob wrote:ah-ha. Thanks Imolavirus. I'm not that interested in the manual boost controller. But where would I find a TCD and how easy are they to fit? Appreciate your help. Still trying to get out to do that run with group 003....

To use the Throttle Cut Defender, you MUST use an MBC as well...no excpetions.

With the MBC setup in parallel...it doesn't actually control the boost. It only limits the spikes. It allows you to set the boost peak where you want while the ECU and N75 still have complete control over the curve.

Rob, have you checked for boost leaks, as the Revo software shouldn't spike like that - very strange that you don't get any errors with 'overboost' symptoms - normally you would get "boost deviation exceeded" or something like that.

You might want to build one of these .... http://www.audisport-iberica.com/ftp_as ... esting.pdf

Nige.

Nige - top man. Thanks. I'll do that today. I was surprised that the software was doing strange things as before having the software installed the car was great and had no spikes running std boost. Running 1.6 bar boost is not my intention so this may very well prove something else underlying.

In addition to that I ran the car last night and got some strange results, it looks like the timing (BTDC) is dropping off something silly after a "hiccup". Basically I logged output from 3 channels and floored the throttle, when the car "jumped" I hit the mark button to try and get a marker of where things were going pete tong, its not very scientific but was giving me a ball park snapshot of what was going on. ImolaVirus mentioned something about throttle cut off, that looks not to be the issue, the throttle drive remains at 100% throughout the "hiccuping". I have turned N75 right down to reduce max boost, but this was getting upto 1.6 bar beforehand. Cut and paste into notepad, save as .csv file and open in Excel. Markers indictate areas where the car "hiccuped" to a larger or lesser degree.

,,Engine speed,Mass air flow,Throttle angle,Ign timing,Engine load,Throttle Drive,Spec'd Boost,Actual Boost
,TIME,,g/s,0-5deg=closed,deg,,,990-1800 mbar,<=1800 mbar
MARKER,STAMP, /min, g/s,%, °BTDC,%,%, mbar, mbar
,35.6,2320,50.53,23.1,27.8,91.7,90.2,990,1030
,36.5,2880,118.67,100,18.8,152.6,100,2070,1250
,37.41,3880,220.14,100,6,185.7,100,2140,1960
1,38.37,4960,248.92,100,5.3,166.9,100,2120,2090
,39.43,5920,124.47,30.6,27,9,5.9,1740,1820
,40.45,4520,15.22,7.1,14.3,12,6.3,990,1100

,68.7,2920,19.08,8.6,39,22.6,8.6,990,1000
,69.6,2960,60.28,22.7,31.5,104.5,100,990,990
2,70.62,3800,210.19,100,12.8,179.7,100,2150,1530
3,71.57,4680,32.56,11.8,7.5,15,7.8,2170,2130
,72.52,4600,15.06,6.7,20.3,11.3,6.7,990,1090
,73.47,4240,14.19,6.3,13.5,10.5,6.3,990,1030

,137.53,1760,37.44,19.6,24.8,81.2,56.5,990,1020
,138.44,2000,57.56,29.8,18.8,89.5,22.7,1450,1120
6,139.34,2320,92.94,92.9,13.5,144.4,98,2160,1270
,140.25,2800,151.64,100,3.8,191.7,100,2010,1720
,141.25,3400,206.81,100,4.5,191.7,100,2080,2280
,142.16,3960,215.56,100,9,183.5,100,2110,2130
7,143.09,4440,238.94,100,2.3,149.6,40.4,2120,2090
,144.04,4520,9.75,5.5,40.5,9.8,5.9,990,1400
,144.99,4400,13.33,5.9,13.5,10.5,5.9,990,1050

,337.9,2200,34.56,14.1,27.8,57.1,16.9,990,1040
,338.81,2520,79.42,92.5,24,121.1,100,1140,1030
,339.71,3320,193.86,100,3.8,191.7,100,2090,1610
10,340.63,4720,240.92,100,3,178.9,100,2120,2120
,341.62,5280,240.72,100,10.5,14.3,5.1,1970,1880

S2tuner wrote:Uuuuuuuuh, MBC's and TCD's again, OMG, is this tuning or tinkering or what???????? Tuning means letting the ECU be in control of everything, including boost and throttle control, WTF is this all about with piggyback solutions to fake the ECU into thinking everything is ok????

If you want to tune a car, you have to do it right, if you have to use any of these gizzmos, it means the ECU isn't doing its job properly, and 2.6 Bar on an S4 is just more than plain stupid, not only unsafe for the turbos. If you look at a compressor map for the S4 K03 turbos, you'll see that 2.6 pressure ratio means very low efficiency, which brings you nothing apart from a little more torque. Tuning isn't all about messing around and trying to get the most out of an engine, it does also have to do with knowing what an engine is, how it is supposed to run, thermodynamics, fluids flow, gas flow and so on. If you're trying to do too much, you'll either just simply loose power or turn the engine into a timebomb and eventually blow your turbos.

Some tuners might actually push their software too far just to help you go along the slippery slope of the €xpen$$iv€ upgrades quicker...

HTH,

Mihnea

I agree with you. I wouldn't run that much boost on K03's. However, it isn't always easy to fix software issues.

However, running an MBC in parallel with the N75 is a very useful tool. The ECU and N75 still have complete control over the boost curve. However, you can set the peak boost limit. I can run anything between 8 and 25 psi while still letting the N75 run the show.

Also check the usual suspect - the TBB - it is a weak spot on the S4 and I'd be suprised if Dialynx hadn't checked this already?

What have Revo said?

S2tuner wrote:... and 2.6 Bar on an S4 is just more than plain stupid, not only unsafe for the turbos.

Based on what I've read, a 'reasonable' tune using K03s should take the boost to around 1.3 bar max, because any more is taking the turbos into an area of the compression map which seriously stresses them enough to reduce expected lifetime to an 'unreasonable' level.

Would you agree?